| Objective To investigate the effects of phillyrin (PHN) on dexamethasone (DEX)-induced autophagy and apoptosis of osteoblasts by regulating phosphatidylinositol 3-kinase (PI3K) / serine threonine kinase (AKT) / mammalian target of rapamycin (mTOR) signaling pathway. Methods MC3T3-E1 cells were divided into control group (NOR group), DEX group (10 μmol/L DEX treated MC3T3-E1 cells), L-PHN group (5 μmol/L PHN treated MC3T3-E1 cells), M-PHN group (10 μmol/L PHN treated MC3T3-E1 cells), H-PHN group (20 μmol/L PHN treated MC3T3-E1 cells), and ZSTK474 group (treated with 20 μmol/L PHN and 2 μmol/L ZSTK474, an inhibitor of PI3K/AKT/mTOR signaling pathway). MTT assay was used to detect cytotoxicity and cell viability. The apoptosis of MC3T3-E1 cells was detected with flow cytometry. The autophagosomes were observed with transmission electron microscopy (TEM). Western blotting was used to detect the expression of autophagy, apoptosis, and PI3K/AKT/mTOR pathway related proteins in MC3T3-E1 cells. ALP activity and ALP staining were used to detect the differentiation ability of MC3T3-E1 cells. Results 0-80 μmol/L PHN had no obvious toxic effect on MC3T3-E1 cells. Compared to those in NOR group, the OD570 value, Bcl-2 protein level, p-PI3K/PI3K, p-AKT/AKT, mTOR protein levels, ALP activity, Beclin1, LC3-II/I protein levels, and the number of autophagosomes in DEX group decreased significantly (P<0.05), and the apoptosis rate, Bax, and cleaved Casase-3 increased significantly (P<0.05). Compared to that in DEX group, the level of apoptosis in L-PHN group, M-PHN group, and H-PHN group decreased significantly (P<0.05), and the proliferation activity, autophagy level, osteogenic differentiation ability and pathway protein levels increased significantly (P<0.05). ZSTK474 eliminated the beneficial effects of PHN on MC3T3-E1 cells. Conclusion PHN promotes autophagy of osteoblasts by activating PI3K/AKT/mTOR signaling pathway, and then inhibits apoptosis of osteoblasts. |